A subsea well of the type concerning herein has a production tree located subsea near the sea floor. The tree lands on a wellhead housing located at the upper end of the well. In one type of well, a tubing hanger lands in the tree, and production tubing suspended from the tubing hanger extends into the well. In another type of well, the tubing hanger lands in the wellhead housing, and the tree is installed on the wellhead housing after running the tubing.
Both the tree in the first type and the wellhead housing in the second type have bores containing smoothly polished sealing surfaces. Wear bushings are installed in the bores to avoid damage to the sealing surfaces before installing the tubing hanger. The wear bushing provides protection against damage from drill pipe and other tools, and is removed before installing the tubing hanger.
Many subsea wells produce with natural pressure, but others have insufficient pressure initially or later to flow naturally at adequate rates. Electrical submersible pumps have been installed in surface wells for many years and more recently in subsea wells to pump the well fluid. A typical electrical submersible pump comprises a large electrical motor that secures to the lower end of a centrifugal pump. Normally, the pump assembly is suspended on the production tubing and discharges well fluid into the tubing. A power cable extends from the motor alongside the tubing to the tubing hanger. In the case of a subsea well, the power cable normally terminates at the tubing hanger, and an electrical connection is made between an electrical receptacle on the tubing hanger and a power source on the exterior of the tree.
The wear bushing in the tree or wellhead housing is normally removed prior to running the submersible pump assembly. This removal allows the tubing hanger to land and seal, but it exposes the seal surfaces to possible damage from the pump assembly as it passes through the tree or wellhead housing.